Identification and distribution of Bacillus species in doenjang by whole-cell protein patterns and 16S rRNA gene sequence analysis

Abstract

Many bacteria are involved in fermentation of doenjang and Bacillus species are known to perform significant roles. Although the SDS-PAGE technique has been frequently used for classification and identification of bacteria in various samples, there has been no investigation of the microbial diversity in doenjang. This study aims to investigate the identification and distribution of dominant Bacillus species in doenjang using SDS-PAGE profiles of whole cell proteins and 16S rDNA sequencing. SDS-PAGE of whole cell proteins of the reference Bacillus strains yielded differential banding patterns that could be considered to be highly specific fingerprints. Bacterial strains isolated from doenjang samples were grouped using whole cell protein patterns, which were confirmed by the analysis of 16S rDNA sequencing. B. subtilis was found to be the most dominant strain in most of the samples, and B. licheniformis and B. amyloliquefaciens were less frequently detected. The results obtained in this study showed that a combined identification method, SDS-PAGE patterns of whole cell proteins and subsequent 16S rDNA sequence analysis, could successfully identify Bacillus species isolated from doenjang.